1. Field of the Invention
The present invention relates to an finger operable accumulator release pump which dispenses liquid from a container only after the liquid pressure, developed by operation of the pump, exceeds a predetermined value. Further, this pump stops dispensing liquid when the liquid pressure drops below this predetermined value.
Finger operable liquid dispensing pumps are ordinarily adapted to be mounted on hand-held containers of liquid consumer products and to dispense liquid from these containers. It is often desirable to dispense liquid products, such as window and all-purpose cleaners, insecticides, and other household products, or hair sprays, deodorants, colognes and similar personal products as a fine or atomized spray.
2. Description of the Prior Art
Finger operated pumps which dispense liquids from containers as a fine spray are known. However, these pumps have been characterized by certain drawbacks.
Typically, pumps of this kind include a hollow pump housing which receives a plunger arranged to be depressed against the force of a compressed return spring to drive liquid to a nozzle. In order to atomize or break the liquid into many microscopic droplets and, thus, to achieve the fine spray discharge, nozzles have been designed which induce turbulence in the liquid that passes through them. However, when the plunger is depressed too slowly, liquid can be discharged from even a turbulence-inducing nozzle at pressures which are not sufficient to create the desired degree of atomization. And, in fact, liquid may dribble from the nozzle in large drops or in a slow continuous stream that is not atomized at all.
Moreover, slow depression of the pump plunger often fails to sufficiently pressurize the liquid to clear the nozzle after dispensing is complete. Thus, certain of the liquid products above which have a tendency to dry up may clog the nozzle, preventing it from being properly used at a later time.
Various attempts have been made to solve these problems characteristic of finger operable atomizing pumps. For example, U.S. Pat. No. Re. 28,366 (Pechstein) discloses a pump which includes a pump housing having interconnected upper and lower chambers, the upper chamber having a larger diameter than the lower. Separate pistons are reciprocally mounted in each chamber. The lower piston, which has smaller cross-sectional area than the upper piston, is connected through a lost-motion coupling to a valve member which closes an outlet passage disposed through the upper piston and a compressed return spring urges both pistons upwardly to also close the valve member. When the upper chamber is filled with liquid and when the upper piston is depressed, the lower piston is moved downwardly at a faster rate than the upper piston by the fixed volume of liquid which was initially confined in the upper chamber. This effect is due to the different cross-sectional areas of the respective chambers. Liquid is dispensed through the outlet passage only after the lower piston has moved sufficiently to open the valve member through the lost-motion coupling. The liquid is then forced outwardly by the lower piston which is driven upwardly by the return spring.
The pump disclosed in the Pechstein patent is complex and consequently relatively expensive to make. Further, parts including the second piston, the lost-motion coupling, and valve member are added to the typical pump configuration. Therefore, this pump, too, has certain drawbacks.
Other pumps which attempt to remedy the problems of the typical atomizing pump are manufactured by the Nippon Unijet Co., Ltd, Osaka, Japan and are disclosed in U.S. Pat. No. 3,761,022 and Japanese Pat. No. 725,372.